I have never thought there was a solid "Yes" or "No" answer to this, as you can see by the various answers above. Not all RVs and electrical circuits are made equal.
Now my opinion. the 30 amp CB will do what it is designed to do. Overload it in Amp draw and it will pop. That's a good thing. Now, if the volts start drop, the CB will not trip. That is a problem as many AC are rated at 115 volts +/- 10%. That means low side is 104 volts. Once volts drop below that, heat rises, you start causing damage to the AC (and other items, if in use).
I have had success in running my 15K and 13.5K at the same time, but only in pristine conditions, like a 30 amp CB with nothing else on it, including that 20 amp socket that should not be but sometimes is drawing from the same source. Also, as some mentioned, you need to turn everything else off.
This weekend, I was at a CG, with some friends, which had very old wiring. There were a few of us, which had 30 amp circuits, but we did not know where that went and if there was truly a 200 amp or 400 amp CB down the line. Well I have a PI 50 Amp EMS, I heard my 1 AC kick off and sure enough the whole coach was dead. While I was checking the Kill-A-Watt, the power came back on. I watched the volts start at 113 volts and then drop to 70.9 when my AC came on. My EMS did it's job again, by shutting off the source. Thank you PI for saving me.
I turned of the one AC I was running, started the genny and then turned on both AC for the afternoon heat.
I told the others of what I saw but they insisted that they were fine. One guy had a Fluke and checked his a couple of times but said it was staying at about 113 volts.
MH is at home and I can run both AC and the volts never dip below 118 volts.
I suggest a
PI 50 EMS. With that you do not need a Kill-A-Watt (or voltmeter) to detect the problem. It will tell you about it. The Kill-A-Watt is still a good, live tool.
